The polar fox is a perfectly adapted predator, which developed a whole host of anatomical and behavioral traits to survive harsh weather conditions of circumpolar areas in which it occurs.
It lives in the northern hemisphere, especially in the Arctic tundra biome.
It can be found from Alaska through the northern part of North America, in Greenland and Iceland, in the northern part of Scandinavia, and throughout north Eurasia.
It is the only land mammal found in Iceland.
It arrived in the area at the end of the last ice age, migrating over the frozen sea.
There are five subspecies of the polar fox.
The Pliocene Tibetan fox (Vulpes qiuzhudingi) is considered the ancestor of this species.
The Tibetan highlands experienced Pliocene (5 to 3,6 million years ago) climate conditions similar to those of the tundra and harbored cold-adapted mammals that spread across North America and Eurasia during the Pleistocene era (2,6 million – 11,7 thousand years ago).
Arctic foxes are adapted to harsh and hostile weather conditions.
The difference between their body temperature and the ambient temperature can reach 212 Fahrenheit, so every joule of energy is at a premium. However, polar foxes have developed a host of behaviors that, combined with their other anatomical features, help them survive in the worst weather conditions.
There are two color variants of polar foxes – white and blue.
The white variant is white during winter, but it is brown on the back and light grey on the belly during summer. The blue variant is mostly grey, steel blue, or brown for the whole year. Although the blue allele is dominant over the white allele, 99% of the polar fox population is born with the white variant. Among those two variants, five varieties of coloring can be distinguished – blue, white, beige, sapphire, and shadowy.
Males are slightly bigger than females.
The length of the snout and body of males reaches an average of 55 centimeters, and 52 with females. Males weigh about 3,5 kilograms, and females 2,9 kilograms. The record-holder among polar foxes weighed about 9,4 kilograms.
Although being omnivorous, they feed mainly on small animals.
Their menu consists of lemmings, voles, and other rodents, as well as fish, birds, hares, and eggs. In May and April, polar foxes hunt for baby seals, which are vulnerable at this time. Occasionally, polar fox's diet consists of algae or berries.
Although not as good as the red fox or dog, their hearing is good.
They can hear in the 125 – 16,000 Hz range. They can hear lemmings digging at a depth of 10 – 15 centimeters.
Their sense of smell is exceptional.
They can smell carrion left by polar bears at a distance of 10 to 40 kilometers. They easily sense and find frozen lemmings under the layer of snow up to 77 centimeters thick and smell a seal’s liar under the 150 centimeter of snow.
The basis of their diet is lemmings, whose population is correlated with that of the Arctic foxes.
When food is abundantly available, foxes can give birth to 18 cubs per litter, while when the food is scarce, they may not breed at all.
They are also scavengers.
When they lack food, they feed on carrion. Arctic fox usually finds animals left by other, more dangerous predators, such as wolves or bears.
In extreme situations of food scarcity, they also feed on feces.
They are able to survive harsh winters and food shortages due to their exceptional energy-storing fat tissue. At the beginning of winter, the polar fox can have 3,500 kcal stored fat. An average-sized polar fox needs about 112 kcal per day to survive. Fat building begins during fall when the fox can increase its body weight by more than 50%.
In freezing weather, polar foxes limit their movement and curl up to minimize heat loss.
They hide their head and limbs under their body and adopt the most optimal shape, which has a reduced heat transfer surface area to an absolute minimum.
Polar fox fur provides the best isolation among all mammal furs. They tolerate temperatures down to – 94 Fahrenheit.
They are perfectly anatomically adapted for this. Thick and multi-layered fur provides excellent thermal insulation. Additionally, the polar foxes are the only canines with fur-covered paws. Moreover, the polar fox has a low body area to volume ratio, as evidenced by its compact body shape, short snout and legs, and short, thick ears.
The mating period begins in the spring.
During this time, polar foxes search for a place to start a family. Fertilization occurs in April or May. Arctic foxes are monogamous, and males and females share the care of the offspring.
The pregnancy of Arctic foxes lasts for 52 days.
A litter can contain up to 25 cubs, a record among all mammalian predators. Cubs leave the burrow after 3 – 4 weeks after birth, and the mother stops feeding them with milk after nine weeks.
Arctic fox's burrows are located on hills in unfrozen soil.
A complex of burrows can cover up to 1,000 square meters. Tunneling systems can function for decades and are inhabited by the next generation of foxes. Arctic foxes usually built tunnel's exit on the south side, which lets in more heat.
More important than the proximity to the food source is a solid and secure burrow for polar foxes.
They tend to choose the best shelters for their families, using even red fox's burrows on shared territories. In case of a predator threat, parents relocate their offspring into harder-to-reach parts of the tunnel system.
When food is abundant, polar foxes can join their families to form pack-like structures.
It helps them guard and protect their territory more effectively. In such structures, polygamy is more common.
Most polar foxes do not survive the first year of their lives.
The first breeding farm of polar foxes was established in North America in 1897.
Since then, fox furs became more popular among women, and the fur industry has grown to enormous proportions. There has been a noticeable decline in interest in fur recently, and